It is well-known to mount a timber-working head in the form of a harvesting head to a carrier to perform a number of functions in connection with timber. For example, the head may be used to grapple and fell a standing tree and process the felled tree by delimbing, possibly debarking (depending on the configuration of the head), and cutting a trunk of the tree into logs (e.g., logs of predetermined length). Processing the felled tree typically involves feeding the felled tree in axially opposite directions, as needed, along a feed axis while delimbing the tree using a number of delimb elements such as one or more delimb arms grappling the tree.
A well-known type of delimb system has a left-hand (LH) delimb arm and a right-hand (RH) delimb arm, both of which are pivotally coupled to a frame of the head. A single hydraulic delimb cylinder is operatively coupled to both delimb arms to pivot the delimb arms relative to the frame so as to open and close them. A timing link interconnects the delimb arms so that they open and close together, preventing independent movement of the delimb arms relative to one another. Such coordinated movement of the delimb arms is useful, for example, to facilitate picking up logs from a stack but is less suitable with ill-formed trees such as those with sweep (i.e., variation in the axial linearity of the tree) or other contour irregularities (e.g., bulges, depressions, lack of circularity).